The present invention relates to separation elements useful for separating various components of fluids. More specifically, the present invention relates to a seal structure for sealing adjacent separation elements.
The use of pressure driven fluid separation systems are well known. In such systems, a fluid mixture is passed across the surface of a membrane adapted to act as a selective barrier, permitting some components of the fluid composition to pass through more readily than others.
Hollow fiber and spiral wound membrane arrangements are commonly used in commercial fluid separation processes. The use of spiral wound membranes is advantageous in that it affords a large membrane contact area while permitting a rather small overall containment vessel. A standard way of supplying spiral wound membranes for commercial use is in the form of membrane elements which comprise a section of a permeate tube or conduit around which the membrane is wound. These membrane elements may then be used singly or joined together in series by interconnecting their permeate conduit sections. The usual way to use spiral wound membrane elements is to contain them, either singly or multiple in containment vessels to form fluid separation modules. The modules can, in turn, be used singly or can be conveniently interconnected in series and/or parallel arrangements to provide the desired treatment.
Spiral wound membranes are typically formed by wrapping one or more sheets of membrane material around a central conduit containing holes for recovery of a central permeate stream. Spacers or other devices can be used to maintain feed-retentate channels through which the feed mixture passes and is separated into the retentate component or permeate components that pass through the membrane surface. Examples of spiral wound elements are provided in U.S. Pat. Nos. 5,538,642 and 5,681,467, both of which are incorporated herein by reference.
When multiple membrane elements are used in series within a single module, it is desirable to seal adjacent elements to one another, and particularly the corresponding adjacent permeate tubes to prevent the flow of feed fluid or retentate fluid into the permeate tube. Typically, this is accomplished by the use of a sliding seal arrangement such as that disclosed in U.S. Pat. No. 5,851,267 to Schwartz, incorporated herein by reference. In such a sliding seal arrangement, an interconnect pipe or tube is received within the ends of adjacent permeate tubes of adjacent separation elements. The interconnect pipe defines a pair of spaced apart grooves on the ends thereof that each receive and retain an O-ring. The O-rings are arranged to segregate the permeate and retentate fluids by applying radial pressure between the outer ends of the interconnect pipe and the inner surfaces of the respective permeate tubes. In an additional embodiment, the O-rings are arranged to segregate the permeate and retentate fluids by applying radial pressure between the inside ends of he interconnect pipe and the outer surface of the respective permeate tubes.
U.S. Pat. No. 5,581,267 further discloses a pair of end caps located on the respective ends of the separation membrane. Each end cap defines an inner opening for receiving the permeate tube of the separation element and an outer locking ring for securing adjacent separation elements together. An O-ring is retained on the locking ring to provide a seal at the outer radial periphery of the end caps. This seal is between adjacent end caps and provides a seal to prevent the feed stream or retentate stream from bypassing separation elements by flowing along the pressure vessel wall.
Additional end cap structures are shown in Japanese Publication No. 11207156 wherein the end cap includes an integral interconnect tube having a seal structure disposed on each end for insertion into an adjacent permeate tube. A similar structure is shown in U.S. Pat. No. 6,224,767, incorporated herein by reference. Japanese Publication No. 11267467 also shows an interconnect tube having seals on either end thereof.
In another method of interconnecting the tubes is shown in Japanese Patent No. 2000015064. In this assembly, an interconnection pipe having a variety of inner diameters is used to control the pressure loss in the permeate tube.
Each of these methods requires an interconnect pipe of some sort having a relatively smaller diameter than the permeate tube. Typically the interconnect pipes or tubes are inserted into the ends of adjacent permeate tubes, resulting in increased pressure loss. In an additional embodiment the interconnect pip has a relatively larger diameter than the permeate tube. This arrangement eliminates the pressure lass, but decreases the effective length of each separation element. There are further disadvantages associated with both of these schemes. Upon insertion of the interconnect pipes, the O-rings are subject to deformation or becoming dislodged from the groove, resulting in an ineffective seal. In certain installations of the interconnect pipes of this type, it has been known to add a lubricant to the O-ring to facilitate installation. The lubricant can provide a contamination problem in the permeate stream.
According to the present invention, there is provided a separation element adapted to be joined to an adjacent separation element for placement in a separation module. The separation element comprises a permeable separation body defining a permeate channel in fluid communication with a first side of said separation body for collecting permeate. The separation element further comprises a permeate tube in fluid communication with the permeate channel. The permeate tube extends between first and second ends. A separation element further comprises a retentate channel on a second side of the permeable separation body. The separation element further comprises a seal surface connected with the tube and adapted to engage a sealing member and axially compress the sealing member between the seal surface and a seal surface of adjacent separation elements. This prevents fluid flow from the retentate channel into the permeate tube at the end of the permeate tube.
Accordingly, it is an object of the present invention to provide a seal structure between adjacent separation elements that reduces the number of seal surfaces, thereby reducing the risk of contamination in the permeate stream.
It is another object of the present invention to provide a seal structure between adjacent separation elements connected to the permeate tube that is axially compressed to provide a fluid tight connection between the permeate tubes of adjacent separation elements.
It is another object of the present invention to provide a seal structure between adjacent separation elements that uses the naturally-occurring pressure drop within the feed-retentate channel to provide additional axial compressive force on the seal structure, thereby improving the effectiveness of the seal during operation.
It is another object of the present invention to provide a seal structure that eliminates twisting or sliding of the seal structure during installation of the separation elements into the separation module.
It is another object of the present invention to provide a seal structure that reduces the possibility of deformation of the seal structure during installation of the separation elements into the separation module.
It is another object of the present invention to fix the position of the seal structure to prevent abrasion of the seal structure due to movement of the separation module or seal structure during operation.
It is another object of the present invention to provide a seal structure that does not restrict the fluid flow in the permeate tube.
It is another object of the present invention to provide a seal structure that does not reduce the effective length of the separation elements.
It is another object of the present invention to provide a locking arrangement between adjacent separation elements that secures the separation elements and provides a predetermined amount of axial compression on the seal structure.
It is another object of the present invention to eliminate the need for a lubricant on the seal structure to facilitate installation of the separation elements, thereby eliminating a potential for contamination in the permeate stream.
It is another object of the present invention to provide a sealing structure that increase the useful life of the seal structure.
It is another object of at least one embodiment of the present invention to provide a locking arrangement between adjacent separation elements that provides an audible or tactile indication that the elements are fully locked together.
It is another object of at least one embodiment of the present invention to recess the sealing surface to protect the sealing surface during handling of the separation elements, prior to installation.
It is another object of at least one embodiment of the present invention to provide a groove for receiving and retaining the sealing structure to avoid unintentional loss of the sealing structure.
It is another object of one embodiment of the present invention to provide a permeate interface adapter that includes the same sealing structure used between adjacent separation elements.